The widespread occurrence of molds capable of producing aflatoxins and other mycotoxins place these toxic carcinogenic metabolites in a prominent position among dangerous food contaminants. The role of these mycotoxins as a possible health hazard is given added importance by the fact that they have been found in our food supply at levels which will induce cancer in experimental animals. With the possible exception of aflatoxin B sub 1, we have little information on the toxicity or carcinogenicity of these mold metabolites. Rainbow trout, because of its extreme sensitivity to afloatoxin B sub 1 will be used as model to evaluate the carcinogenic hazard of aflatoxin B sub 2, G sub 1 and G sub 2 and their possible synergistic action with B sub 1. The acute toxicity and carcinogenicity of patulin, sterigmatocystin and the ochratoxins will be quantitatively examined. The preparation of C14 ochratoxins and patulin, their excretion and tissue distribution will be determined. Other mold metabolites which may plausibly contaminate food have been demonstrated to occur in food or feedstuffs will be evaluated for carcinogenicity with the trout system.